Before being assembled into something recognisable at a museum, most dinosaur fossils look to the casual observer like nothing more than common rocks. No one, however, would confuse the over 110 million-year-old nodosaur fossil for a stone.

The fossil, being unveiled today in Canada's Royal Tyrrell Museum of Paleontology, is so well preserved it looks like a statue, reported the Washington Post.

Even more surprising might be its accidental discovery, as unveiled in the June issue of National Geographic magazine.

On March 21, 2011, Shawn Funk was digging in Alberta's Millennium Mine with a mechanical backhoe, when he hit "something much harder than the surrounding rock". A closer look revealed something that looked like no rock Funk had ever seen, just "row after row of sandy brown disks, each ringed in gunmetal grey stone".

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What he had found was a 1130kg dinosaur fossil, which was soon shipped to the museum in Alberta, where technicians scraped extraneous rock from the fossilised bone and experts examined the specimen.

A close-up of the nodosaur fossil. The dinosaur's head is clearly visible. Photo / Robert Clark, National Geographic
A close-up of the nodosaur fossil. The dinosaur's head is clearly visible. Photo / Robert Clark, National Geographic

"I couldn't believe my eyes - it was a dinosaur," Donald Henderson, the curator of dinosaurs at the museum, told Alberta Oil. "When we first saw the pictures we were convinced we were going to see another plesiosaur (a more commonly discovered marine reptile)."

More specifically, it was the snout-to-hips portion of a nodosaur, a "member of the heavily-armoured ankylosaur subgroup" that roamed during the Cretaceous Period, according to Smithsonian. This group of heavy herbivores, which walked on four legs, likely resembled a cross between a lizard and a lion - but covered in scales.

Unlike its cousins in the ankylosaur subgroup, the nodosaur lacked a bony club at the end of its tail, instead using armour plates, thick knobs and two 20-inch spikes along its armoured side for protection, according to the Smithsonian Museum of Natural History.

"These guys were like four-footed tanks," dinosaur tracker Ray Stanford told The Washington Post in 2012.

This particular one, according to a news release, was 5.5 metres long and weighed around 1360kg.

A model showing how the nodosaur likely appeared. Photo / Robert Clark, National Geographic
A model showing how the nodosaur likely appeared. Photo / Robert Clark, National Geographic

As Michael Greshko wrote for National Geographic, such level of preservation "is as rare as winning the lottery". He continued:

"The more I look at it, the more mind-boggling it becomes. Fossilised remnants of skin still cover the bumpy armour plates dotting the animal's skull. Its right forefoot lies by its side, its five digits splayed upward. I can count the scales on its sole."

Caleb Brown, a postdoctoral researcher at the museum, grins at my astonishment. "We don't just have a skeleton," he tells me later. "We have a dinosaur as it would have been."

The reason this particular dinosaur was so well preserved is likely due to a stroke of good luck. (Well, perhaps a stroke of bad luck for the poor nodosaur).

Researchers believe it was on a river's edge, perhaps having a drink of water, when a flood swept it downriver.

Eventually, the land creature floated out to the sea - which the mine where it was found once was - and sank to the bottom.

There, minerals quickly "infiltrated the skin and armour and cradled its back, ensuring that the dead nodosaur would keep its true-to-life form as eons' worth of rock piled atop it".

That is a boon to researchers, particularly given that teeth and bone fragments are much more common finds.

"Even partially complete skeletons remain elusive," the Smithsonian reported.